I brought Autumn Joy sedum from Maryland when we moved to NC several years ago. I had several plants I put in the ground plus a few in containers. I saw the birds eating pieces of leaves from a container on my deck. Every year the sedum starts to grow and then they eat it clear to the ground. It may start to grow again in late summer but they still chew it up. I have bird feeders and water so I agree that it must be the taste of the leaves. Whether the sedum is a big one or smaller ground cover, and whether in the ground or a pot, if it is visible it gets chewed to the ground.